The Impossible Game is anything but 'Impossible', and in some of the worst ways. The first of which is that this game isn't actually hard, challenging or difficult. It's artificially Difficult. The levels and mechanics are designed to give you a very small window to correctly execute what's required, often not enough for you to be able to react fast enough on the first try. There is not much actual skill required to beat this game, nor is it challenging, it's just a test of muscle memory. The only real way to play is to keep trying and dying in a level until you can remember what exactly to do. Couple that with the fact that dying sends you completely back to the start of a decently sized static level, you'll only find yourself getting frustrated at the game while slowly trying to get back to where you were to have another shot. If you're getting upset over the game instead of your own lack of skill, there's clearly something wrong.
Secondly, the port to PC is pretty bad. I've checked around the Steam Discussions and found mixed results, but there are clearly people experiencing troubles with the game, and there's no fix in sight. I personally experience some of the worst stuttering and motion blur I've ever seen in a game before, I literally have to play the game on the smallest resolution to make it even bearable to play for smaller play sessions, and that's completely dodging how hard it is to actually play the game while trying to focus on such a blurry mess. It's certainly not a problem with my monitor though, as when recording the game, the footage catches both the blur and the stuttering, which you can see in the video posted in the next point.
Finally, but most importantly, the game isn't even consistent! By far the worst part about the game is how random the hitboxes for the spikes are. I literally have recorded footage of the cube going half way into a spike and surviving while other times getting kill by the mere edge of the spike. I find it pretty hard to recommend any game with such ridiculously inconsistent hitboxes, especially when spikes are practically half of what this entire game is. Seriously though, I actually have a recording of this: https://www.youtube.com/watch?v=8-urtO-0R84
In all honesty, it's certainly a nice idea, and I was really hoping it'd be better, but It just didn't come together properly. Short of that though, the controls are tight, and it's undeniably fun to glide through a level nailing everything nicely, but with the game being built around artificial difficulty in such a way that encourages frustration, it's certainly isn't the most fun game you could buy. The best part of this game is easily the music, but that's all downloadable for free on the Newgrounds Audio Portal.
If all that doesn't sound too bad, you probably will enjoy the game for what it is, but I'd highly recommend you take your $5 and buy Super Hexagon instead.